EmuDuration.hh

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#ifndef EMUDURATION_HH
#define EMUDURATION_HH
 
#include "narrow.hh"
#include "serialize.hh"
#include <cassert>
#include <concepts>
#include <cstdint>
#include <limits>
#include <type_traits>
 
namespace openmsx {
 
// constants
inline constexpr uint64_t MAIN_FREQ = 3579545ULL * 960;
inline constexpr unsigned MAIN_FREQ32 = MAIN_FREQ;
static_assert(MAIN_FREQ < (1ULL << 32), "must fit in 32 bit");
inline constexpr double RECIP_MAIN_FREQ = 1.0 / MAIN_FREQ;
 
 
class EmuDuration
{
public:
        // This is only a very small class (one 64-bit member). On 64-bit CPUs
        // it's cheaper to pass this by value. On 32-bit CPUs pass-by-reference
        // is cheaper.
#ifdef __x86_64
        using param = EmuDuration;
#else
        using param = const EmuDuration&;
#endif
 
        // friends
        friend class EmuTime;
 
        // constructors
        constexpr EmuDuration() = default;
        constexpr explicit EmuDuration(uint64_t n) : time(n) {}
        constexpr explicit EmuDuration(double duration)
                : time(uint64_t(duration * MAIN_FREQ + 0.5)) {}
 
        static constexpr EmuDuration sec(unsigned x)
                { return EmuDuration(x * MAIN_FREQ); }
        static constexpr EmuDuration msec(unsigned x)
                { return EmuDuration(x * MAIN_FREQ / 1000); }
        static constexpr EmuDuration usec(unsigned x)
                { return EmuDuration(x * MAIN_FREQ / 1000000); }
        static constexpr EmuDuration hz(unsigned x)
                { return EmuDuration(MAIN_FREQ / x); }
 
        // conversions
        [[nodiscard]] constexpr double toDouble() const { return double(time) * RECIP_MAIN_FREQ; }
        [[nodiscard]] constexpr uint64_t length() const { return time; }
 
        // comparison operators
        [[nodiscard]] constexpr auto operator<=>(const EmuDuration&) const = default;
 
        // arithmetic operators
        [[nodiscard]] constexpr EmuDuration operator%(EmuDuration::param d) const
                { return EmuDuration(time % d.time); }
        [[nodiscard]] constexpr EmuDuration operator+(EmuDuration::param d) const
                { return EmuDuration(time + d.time); }
        [[nodiscard]] constexpr EmuDuration operator*(uint64_t fact) const
                { return EmuDuration(time * fact); }
        [[nodiscard]] constexpr EmuDuration operator/(unsigned fact) const
                { return EmuDuration(time / fact); }
        [[nodiscard]] constexpr EmuDuration divRoundUp(unsigned fact) const
                { return EmuDuration((time + fact - 1) / fact); }
        [[nodiscard]] constexpr unsigned operator/(EmuDuration::param d) const
        {
                uint64_t result = time / d.time;
#ifdef DEBUG
                // we don't even want this overhead in devel builds
                assert(result == unsigned(result));
#endif
                return unsigned(result);
        }
        [[nodiscard]] constexpr unsigned divUp(EmuDuration::param d) const {
                uint64_t result = (time + d.time - 1) / d.time;
#ifdef DEBUG
                assert(result == unsigned(result));
#endif
                return unsigned(result);
        }
        [[nodiscard]] constexpr double div(EmuDuration::param d) const
                { return narrow_cast<double>(time) / narrow_cast<double>(d.time); }
 
        constexpr EmuDuration& operator*=(unsigned fact)
                { time *= fact; return *this; }
        constexpr EmuDuration& operator*=(double fact)
                { time = narrow_cast<uint64_t>(narrow_cast<double>(time) * fact); return *this; }
        constexpr EmuDuration& operator/=(double fact)
                { time = narrow_cast<uint64_t>(narrow_cast<double>(time) / fact); return *this; }
 
        // The smallest duration larger than zero
        [[nodiscard]] static constexpr EmuDuration epsilon() {
                return EmuDuration(uint64_t(1));
        }
 
        // ticks
        // TODO: Used in WavAudioInput. Keep or use DynamicClock instead?
        [[nodiscard]] constexpr unsigned getTicksAt(unsigned freq) const
        {
                uint64_t result = time / (MAIN_FREQ32 / freq);
#ifdef DEBUG
                // we don't even want this overhead in devel builds
                assert(result == unsigned(result));
#endif
                return unsigned(result);
        }
 
        [[nodiscard]] static constexpr EmuDuration zero()
        {
                return EmuDuration(uint64_t(0));
        }
 
        [[nodiscard]] static constexpr EmuDuration infinity()
        {
                return EmuDuration(std::numeric_limits<uint64_t>::max());
        }
 
        template<typename Archive>
        void serialize(Archive& ar, unsigned /*version*/)
        {
                ar.serialize("time", time);
        }
 
private:
        uint64_t time = 0;
};
 
template<> struct SerializeAsMemcpy<EmuDuration> : std::true_type {};
 
 
template<std::unsigned_integral T> class EmuDurationCompactStorage
{
public:
        explicit constexpr EmuDurationCompactStorage(EmuDuration e)
                : time(T(e.length()))
        {
                assert(e.length() <= std::numeric_limits<T>::max());
        }
 
        [[nodiscard]] explicit constexpr operator EmuDuration() const
        {
                return EmuDuration(uint64_t(time));
        }
private:
        T time;
};
 
using EmuDuration32 = EmuDurationCompactStorage<uint32_t>;
using EmuDuration16 = EmuDurationCompactStorage<uint16_t>;
using EmuDuration8  = EmuDurationCompactStorage<uint8_t>;
 
namespace detail {
        // via intermediate variable to work around gcc-10 warning
        inline constexpr uint64_t max32 = std::numeric_limits<uint32_t>::max();
        inline constexpr uint64_t max16 = std::numeric_limits<uint16_t>::max();
        inline constexpr uint64_t max8  = std::numeric_limits<uint8_t >::max();
}
template<uint64_t MAX>
using EmuDurationStorageFor = std::conditional_t<(MAX > detail::max32), EmuDuration,
                              std::conditional_t<(MAX > detail::max16), EmuDuration32,
                              std::conditional_t<(MAX > detail::max8 ), EmuDuration16,
                                                                        EmuDuration8>>>;
} // namespace openmsx
 
#endif